The invention relates to a data display for a strobo unit.
The illumination of a strobo unit can be controlled in the following three manners: (1) the duration of the flash from the strobo unit may be maintained constant while a diaphragm aperture on the part of a camera can be controlled in accordance with the relationship between a guide number and a distance (this being referred to as a manual control); (2) a light receiving element may be disposed in one unit with the strobo unit for determination of an external light, and the output signal from the element is used to control the duration of the flash from the strobo unit (hereafter referred to as an automatic control); and (3) a light receiving element may be disposed within a camera for receiving reflected light from a shutter blade or a film surface, and the output signal from the element is used to control the duration of the flash from the strobo unit (hereafter referred to as TTL control).
An arrangement used for performing the automatic control is commonly referred to as an automatically controlled strobo unit or auto strobo. This comprises a light receiving element which is disposed either in one unit with the strobo unit or detachably mounted on the strobo unit or on the external portion of the camera body. Light from an object being photographed directly impinges on the element, which produces an output signal to provide an automatic control of the duration of the flash. However, the automatic control suffers from certain difficulties in that a diaphragm aperture on the part of the camera is limited to a particular range and that an error may be caused in the control of the flash time because of the photometry which is directed not to light paassing through the taking lens. These difficulties can be overcome by the provision of a light receiving element within the body of the camera for receiving reflected light from a shutter blade or a film surface in order to control the flash time in accordance with an output signal from this element. This type of control is known as the TTL control which is most ideal in providng a proper exposure. However, the TTL control can only be utilized in a camera which is provided with a light receiving element in the interior thereof.
On the other hand, it will be appreciated that it is sometimes more appropriate, depending on the type of objects being photographed, to determine a diaphragm aperture by a manual control or in accordance with the relationship between the guide number and the distance.
In view of the foregoing, it is desirable to provide a strobo unit which can be operated according to either one of the manual, automatic or TTL control and to enable a particular one of these control schemes depending on a particular situation of taking pictures. This, however, entails the necessity to display various data involved with the individual control schemes. There has been no strobo unit which includes a combination of these three types of strobo controlling devices, principally because of the difficulty encountered in presenting different kinds of data which are associated with these control schemes.